Nutrient media formulations have been used to cultivate a number of cell types including animal, plant and microbial cells. Cells cultivated in culture media catabolize available nutrients and produce useful biological substances such as monoclonal antibodies, hormones, growth factors, viruses and the like. Such products have therapeutic applications and, with the advent of recombinant DNA technology, cells can be engineered to produce large quantities of these products. Thus, the ability to cultivate cells in vitro is not only important for the study of cell physiology, but is also necessary for the production of useful substances which may not otherwise be obtained by cost-effective means.
Typical components of microbial culture media may include protein hydrolysates, inorganic salts, vitamins, trace metals, and carbohydrates, the types and amounts of which may vary depending upon the particular requirements of a given species of microorganism. Because these components tend to be more stable in a dehydrated form, they are frequently provided as dry, powdered formulations. The powdered formulations are added to water and, optionally, sterilized before use.
Culture media are typically produced in liquid form or in powdered form. Each of these forms has particular advantages and disadvantages.
For example, liquid culture medium has the advantage that it is provided ready-to-use (unless supplementation with nutrients or other components is necessary), and that the formulations have been optimized for particular cell types. Liquid media have the disadvantages, however, that they may require the addition of supplements (e.g., a vitamin or cofactor, and antibiotic) for optimal performance in cultivating a particular microorganism. Furthermore, most liquid media require some type of sterilization (e.g., autoclaving, filtration), which can be a time-consuming and/or expensive process.
To overcome some of the disadvantages, liquid culture medium can be made in concentrated form; the concentrate may be diluted to working concentrations prior to use. This approach provides the capability of making larger and variable batch sizes than with standard culture media, and the concentrated media formulations or components thereof often have longer shelf-life. U.S. Pat. No. 5,474,931 is directed to culture media concentrate technology and is incorporated herein by reference in its entirety. Despite these advantages, however, concentrated liquid media still have the disadvantages of their need for the addition of supplements, and may be difficult to sterilize economically.
As an alternative to liquid media, powdered culture media are often used. This approach has the advantages that larger batch sizes may be produced, the powdered media typically have longer shelf lives than liquid media, and the media can be sterilized by irradiation (e.g., gamma or ultraviolet irradiation) or ethylene oxide permeation after formulation. However, powdered media have several distinct disadvantages. For example, some of the components of powdered media become insoluble or aggregate upon lyophilization such that resolubilization is difficult or impossible. Furthermore, powdered media typically comprise fine dust particles which can make them particularly difficult to transfer and/or reconstitute without some loss of material, and which may further make them impractical for use in many biotechnology production facilities operating under GMP/GLP, USP or ISO 9000 settings.
Despite the advancements in rehydratable media, there still exists a need for rapidly dissolving nutritionally complex stable dry powder nutritive media, media supplements, media subgroups and buffers, which can be prepared in variable bulk quantities and which are amenable to sterilization.